For young banded mongoose moms, there’s only one choice for when to give birth — the same day as older, dominant mothers. In communities of these cat-sized animals, all females give birth together, no matter when they became pregnant.

It’s in the subordinate mongoose’s best interest to synchronize labor to give her young their best chance at survival, researchers now report. When scientists used contraceptives to manipulate mongoose pregnancy, they found that dominant females would kill any ne...